Apparatus for separation and fractionation of material suspended in a liquid

ABSTRACT

APPARATUS FOR SEPARATION AND FRACTIONATION OF MATERIAL SUSPENDED IN A LIQUID HAS A PLURALITY OF HELICAL PASSAGEWAYS, PERFERABLY IN FLAT SPIRAL FORM, CONCENTRICALLY MOUNTED AS A UNIT WHICH IS ROTATED TO PICK UP PLUGS OF LIQUID AND ANOTHER PHASE ALTERNATELY AND DISCHARGE THE LIQUID PLUGS INTO SEPARATE RECEIVERS. IDENTICAL UNITS ARE MOUNTED SIDE BY SIDE AS AN ASSEMBLY WITH ALL DISCHARGING INTO THE SAME RECEIVERS. THE CROSS SECTIONAL AREA OF THE PASSAGEWAY IS REDUCED FROM INLET TO OUTLET, PREFERABLY REGULARLY AND CONTINUOUSLY, TO IMPROVE THE TENDENCY OF PARTICLES OF LARGER SIZE TO CONCENTRATE PROGRESSIVELY AT THE FRONT END OF THE LIQUID PLUB. THE AREA REDUCTION MAY ALSO BY BY ABRUPT NARROWING AS BY A LONGITUDINAL PARTITION PLACED IN THE PASSAGEWAY PART WAY ALONG ITS LENGTH.

OC. 26,1971 G OLGARD 3,615,020

APPARATUS FOR SEPARATIN AND FRACTIONATION Ul" MA'll-RI'AL SUSPENDED IN A LIQUID Filed Oct; G, 1969 3 Sheets-Sheet 7|.

FIG/1A :Nwe/vrou. Gunnar O/grd By Dov/s, Hex/19, Fa/'fhfu/l 8 Hapgood After/lays FIG.5

Oct. 26,1971

ined oct e 1969 c;i oLGARn 3,615,020 APPARATUS FOR SEPARATION AND FRACTIONATION OF MATERIAL SUSPENDED IN A LIQUID 3 Sheets-Sheet 2 .0 .'00 NMJam W O H 0 N foo# UM nm U 6M, m

Oct. 26, 1971 OLGARD 3,615,020

G. APPARATUS FOB SEPARATION AND FRACTIONATION OF MATERIAL SUSPENDED IN A LIQUID Filed lOct. 6, 1969 l 5 Sheets-Sheet 5 C) bvgbq) Q E ANN INVENTOR.

Gunnar O/grd 5y Dawg/10x13 Fa//hfw/ Hapgood Attorneys United States 3,615,020 APPARATUS FOR SEPARATION AND FRAC'IINA- TION F MATERIAL SUSPENDED IN A LIQUID Gunnar Olgard, Nynashamn, Sweden, assgnor to Rederiaktiebolaget Nordstjernan Filed Oct. 6, 1969, Ser. No. 863,847

Claims priority, application Sweden, Oct. 7, 1968,

13,497/ 68 Int. Cl. B01d 43/ 00 U.S. Cl. 210-322 17 Claims ABSTRACT 0F THE DISCLOSURE Apparatus for separation and fractionation of material suspended in a liquid has a plurality of helical passageways, preferably in flat spiral form, concentrically mounted as a unit which is rotated to pick up plugs of liquid and another phase alternately and discharge the liquid plugs into separate receivers. Identical units are mounted side by side as an assembly with all discharging into the same receivers. The cross sectional area of the passageway is reduced from inlet to outlet, preferably regularly and continuously, to improve the tendency of particles of larger size to concentrate progressively at the front end of the liquid plug. The area reduction may also be by abrupt narrowing as by a longitudinal partition placed in the passageway part way along its length.

This invention relates to apparatus for separating and fractionating material carried or suspended in a liquid. The invention is an improvement upon the invention disclosed in U.S. Letters Pat. 3,396,850 issued Aug. 13, 196,8. More particularly, this invention relates to such apparatus utilizing a concentrating effect obtained by relative motion between a liquid and its container or passageway walls. In the particular type of apparatus to which this invention relates, plugs of the liquid pass along a passageway in spaced relation during which the suspended material becomes concentrated in the front portion (measured in the direction of flow) of each plug of liquid, with the larger particles nearest the front and progressively smaller particles toward the rear of plug, according to known phenomena. Usually the liquid plugs are spaced by another phase, e.g. a gas, which most commonly is air. When air is referred to herein it will be understood to include all equivalents of said other phase.

According to the present invention spaced plugs of the liquid to be treated pass along a passageway whose cross sectional area varies continuously at least along a substantial part of its length to enable control of the separation and fractionation from the liquid of particles of different sizes.

The passageway may converge from its feed end to its discharge end by having its cross sectional area gradually and progressively decrease in size, to facilitate separation of the greatest particles rst and separation thereafter of the smaller particles, and also to allow back-ilushing from the discharge end to loosen and flush rearwards 'any cloggings which might possibly have formed.

Also according to the invention when the suspension contains mostly small particles and only a relatively few large ones, the area of the passageway may be abruptly decreased at a predetermined distance from the feed end to increase the effect of progressive concentration of different sized particles by inserting a partition wall in and parallel to, and between the helical walls of each passageway.

Also according to the invention the cross sectional area of the passageway may be abruptly enlarged at a Patent ICC predetermined distance from its feed end to eliminate risk of clogging which may be more acute when some suspensions are being processed, by merging or combing one or more adjacent passageways at a predetermined distance from the entrance end, forming a joint or combined enlarged passageway from that point onward. This arrangement is particularly suitable when longbred and short-bred particles are to be separated. The plug in passing into the enlarged section breaks up and ycauses separation of the long and short libres so that the short fibres can travel rearward.

Also according to the invention the passageway preferably is in the form of a ilat helix or spiral and is rotated about an axis perpendicular to its plane and passing through its center, with the feed entrance near the axis of rotation and the discharge end located at the peripheral end of the helix in position to discharge into a fraction collector.

This arrangement enables the apparatus to be simple and compact and efficient.

Also according to the invention there may be a plurality of `concentric helical or spiral passageways interleaved in the same plane forming a unit, with the entrances (and likewise the exits) of bhe several interleaved passages being angularly spaced from each other around the unit.

Also 'a plurality of such units preferably are located side by side along the same axis, to increase the capacity and compactness of the installation.

Other advantages and the objects of the invention will appear `as the invention is described in connection with the drawings.

'In the drawings FIG. 1 is a side elevation view partly broken away of apparatus embodying one form of the invention.

FIG. 2 is an end elevation of the apparatus of FIG. l.

FIG. 3 is a transverse vertical section view along line 3h-3` of FIG. l showing diagrammati-cally one unit of the apparatus of FIG. l.

FIG. 4 is a radial section view of one half of the unit of FIG. 3.

FIG. 5 is a view similar to FIG. 3 of a second form of the passageways according to the invention, showing two passageways of one unit merging at a certain distance from the entrance end.

FIG. 6 is a view similar to FIG. 5 of third form showing a partition inserted along the length of a passage.

Referring to the drawings, the separation and fractionating apparatus comprises a hollow casing 10 of configuration to rotatably support a rotary assembly, designated generally by the numeral 20 made up of a plurality of identical flat units secured together in side by side relationship, the units being designated generally by numeral 30, and being described in detail below.

The casing may be made in generally circular or cylindrical shape with closed ends 12' and 14 having axial extensions 12a, 14a to accommodate a hydraulic motor 15 or some other drive in one extension 12a and a liquid inlet pipe or duct 16 in the other extension 14a.. Although a hydraulic motor is a convenient motive means other exterior motor means may be employed if desired. The casing may have several radially extending pockets or receptacles 17a, 17b, 17C formed in a lower quadrant (the lower right quadrant as viewed in FIG. 2 when the rotation of the rotary unit assembly is clockwise in FIGS. 2 and 3), to receive the different fractions of separated material issuing from the units, as more fully described below. Three pockets 17a, 17b, 17C are shown in FIG. Z but a different number may be provided as different liquid suspensions and different usages require.

The individual units which make up the rotary assembly may each comprise a circular flat plate or disc 31 having mounted edgewise on one face a plurality of continuous concentric spiral walls 32a to 32f which are spaced apart equally and start their outward spiral courses at points which are spaced angularly around the periphery of a central circular aperture 31a in the disc 31. Although six spiral walls are shown there may be more or less depending on the size of the apparatus, its intended usage and the composition of the liquids to be processed.

The distance that the Walls extend perpendicularly from the face of the plate may be from about 1/2 inch to two inches, in most cases.

IIt will be seen that each of the concentric spiral walls forms between itself and the next wall a spiral passageway; and a plurality of concentric spiral passageways A to F are thus formed equal in number to the number of walls. Each passageway is bounded by two concentric spiral walls and by the disc on whichthey are mounted and by the disc of the adjacent unit. The spirality of each individual wall is arranged so that each convolution of that spiral is slightly closer to the previous convolution than its predecessor was to the convolution that preceded it. Thus, the cross sectional area of each spiral passageway decreases as the spiral proceeds from the center outwards. In other words each passageway is convergent in its outward course. Preferably the cross section at the mid-point along the passageway will be square. T'he areas of each of the six passageways measured at any radial angle and at any chosen convolution of the six (c g., the third convolution at a 120 angle) is equal so that uniform actions and results will be obtained from each of the concentric spiral passageways of a unit, and likewise from all the units.

The central openings through the many side-by-side units of the rotary assembly combine to form a central tubular passage 312, for convenience called a tube herein, through all the units. The diameter of the tube should be suficient to contain an amount of incoming liquid at a substantially constant level, less than full capacity, as the liquid is withdrawn. Preferably the liquid level is maintained at between 90 and slightly above 200 measured as a sector angle of the liquid level in the tube.

Vlt will be noted that as the assembly is rotated in a direction opposite to the outward course of the spiral passages, liquid is picked up as the inner end of a passageway goes down into the liquid in the central tube. This continues until that inner end rises above the surface of the liquid in the tube. The plug of liquid thus picked up moves along that passageway as the assembly rotates, until the inner end of the passageway again reaches the surface of the liquid in the tube. Meantime a plug of air has formed in the passageway. Then the process repeats itself providing in the passageway a series of plugs of liquid separated by plugs of air. The same happens in all passageways. The length of the entering liquid plug will be approximately equal to the sector angle of the liquid level; and the length of the air plug will be 360 minus said sector angle. If the assembly were at rest the liquid plug would lie in the lower half of the passageway. When rotation clockwise (for example) starts, the liquid plug moves clockwise to a position determined by the liquid friction against the passageway walls.

The friction of the walls of the passages on the liquid plug tends to cause the suspended particles of larger size to move to the front of the plug and progressively the particles are distributed along the length of the plug in proportion to the size of the particles with those of less size at the rear.

This phenomena is greatly favored by the reduction in area of the passageways from entrance to exit, for the following reason:

The characteristic measure of the passageway can be said to be the so-called hydraulic diameter, i.e., the cross sectional area of the passageway divided by the circumference of the passageway. It has been found that the 4 greater the ratio between the particle size and the hydraulic diameter the better the separation.

As the liquid plugs are transported along the convergent passageways they become elongated and their diameter decreases.

Thus, the separation effect and the ultimate collection of the fractions separately, is constantly and greatly improved by the continued convergence of the passageways.

The pressure in the air plugs remains constant during the transport of the liquid plugs, irrespective of whether the transport is directed radially outward as illustrated, or inwards as may be possible in an alternate practice of the principle of the invention.

The units 30 are assembled and secured between circular end plates 22, 24 which rotate in bearings 25, preferably cushion-mounted ball bearings supported from the casing, and are driven by motor 15 which is connected coaxially with the unit assembly. To keep the liquid within the tube 311* prior to treatment, a suitable membrane or closure plate 25 may be provided adjacent the motor connection to the rotary assembly, and suitable plates 26 and packing may likewise be provided at the opposite or liquid inlet side.

In order to maintain the liquid in the tube 31t at the desired level, an overflow passage 27 may be provided in the end plate 14 with its mo'uth (not visible) at the desired level and its outlet 28 conveniently placed to return the liquid to the supply (not shown).

Obviously the details of design, form, and location of the casing, motor, bearings and liquid inlet passages are subject to many variations which will occur to those skilled in the art, and they need not be illustrated nor described.

For collecting the fractions of different concentrations of suspended material from the liquid plugs, the three previously mentioned pockets 17a, 17b, 17C are provided. Although three pockets are shown in FIG. 2 a different number may be provided if ditferent liquid suspensions and different usages require.

The fractions are drained off through outlets, such as 18, from the individual pockets.

As the rotary assembly turns clockwise in FIGS. 2 and 3 the outlet ends A to F of the assembly at its periphery reach a point in the lower right quadrant Where the liquid plugs flow out. For example, if a plug starts to discharge in the position where outlet C is shown in FIG. 3, the forward end of the plug containing the largest particles will discharge into pocket 17a (FIG. 2), the mid-portion of the plug will discharge into pocket 17b and the back portion of the plug containing the smallest particles will discharge into pocket 17C. In-between portions will flow into the next lower pocket, so that the rst pocket available to receive any such portions discharged in between, will always receive the largest remaining particles from the plug.

During one revolution of the assembly one liquid plug is discharged from each unit and this occurs during rotation through the angle of discharge, i.e., from just above the pocket 17a until just past the pocket 17C, so that the first and last portions of the plug will run into the rst and last pockets. Following each liquid plug is an air plug occupying the passageway until on the next revolution, discharge of another liquid plug takes place.

The convergence of the passageway has another advantage in that it allows back-flushing to loosen or remove possible cloggings within the passageways.

Preferably, the passageways are so designed that within the boundaries of any sector, irrespective of where taken from the center of the tubular passage to the periphery rotary assembly, referring to FIG. l, the volume of every individual passageway will be constant and equal. Thus as the plug lengthens with reduction of the area of the individual passageway as it proceeds from entrance to exit, the same volume will be contained in all the convolutions within the boundaries of said sector.

As an alternative, a partition wall 46 may be inserted as shown in FIG. 6 in individual passageways 45 between the walls of each passageway at a predetermined point along its length, which has the effect of reducing the area and providing two smaller parallel passageways. In FIG. 6 only one passageway is shown for simplicity and convenience.

As another alternative after the passageways have proceeded from the inlet end toward the outlet end and have become progressively narrowed to not less than a minimum for the particular suspension which is to be processed, two adjacent passageways may merge as shown at `43 in FIG. 5. In this ligure only two adjacent passageways 42 and 44 are shown for simplicity and convenience. This arrangement is desirable when long-fibred and shortlibred particles are to be separated. The liquid plug breaks up causing separation of the long and short fibers as the plug passes into the merged section allowing the short bred particles of lighter weight to disengage the longer ones and to travel rearward.

The two above described variations in area will preferably be located at least 1/2 a convolution to about 11/2 convolutions from the entrance and if repeated it will be no oftener than 1A. to 11/2 convolutions. Probably most often the positioning would be one convolution. Practical considerations may require greater distances for some liquids.

In the form of the invention illustrated, the discs 31 can not practically be altered from their planar form to vary the size of the passageways along their length. Hence any change in the area when merging two passageways or when inserting a partition will be by change of position of the helical walls as they proceed toward the outlet of the passageways. It is preferable to observe the limits of approximately 1/2 inch up to about 2 inches between the helical walls of a passage when making such variations.

At some sacrice in compactness and loss from a design point of view, the converging passageways need not be in planes perpendicular to the axis but may be helixes running spirally lengthwise of the axis of rotation as in PIG. 7 of Pat. 3,396,850.

From the foregoing, one can understand that the invention in its various forms, has the advantages of spacesaving compactness, ability to cleanse by back-flushing, control of the separation and fractionation effect, adaptability to processing suspensions containing different degrees of the different sizes of particles including long and short fibers, and basic simplicity in principle of operation.

Many modifications within the scope of the invention will occur to those skilled in the art. Therefore, the invention is not limited to the exact form and detail of the embodiments described.

What is claimed is:

1. Apparatus for the separation and fractionation of material suspended in a liquid comprising at least one rotatable unit which includes a passageway in the form of a helix having an inlet end and a discharge end, means t rotate said unit about the axis of said helix and to cause introduction through said inlet end of plugs of said liquid spaced apart by another phase, said passageway having cross sectional area to effectively cause concentration of particles of greater size in the front portion of the liquid plug considered with respect to the direction of movement of the liquid plug and concentration of the particles of lesser size toward the rear of the liquid plug, the cross sectional area of said passageway having a continuously varying area at least along a substantial part of its length to enhance the concentrating effect, and means to collect separately fractions of liquid containing concentrations of particles of progressively smaller size as said liquid plugs are discharged from the passageway of said rotating unit.

2. Apparatus as claimed in claim 1 wherein said cross sectional area is regularly and continuously reduced through the entire length of the passageway.

3. Apparatus as claimed in claim 1 wherein a partition wall is positioned in said passageway running along it and in parallelism within it from an intermediate point to the outlet of the passageway dividing it into two smaller passageways of equal cross sectional area.

4. Apparatus as claimed in claim 1 in which the passageway is defined by plate means perpendicular to said axis, at least two wall means mounted edgewise on said plate means and curved to form between them a passageway in the form of a fiat spiral, and second plate means covering said passageway.

5. Apparatus as claimed in claim 1 wherein said cross sectional area is regularly and continuously reduced through at least a portion of the length of the passageway.

6. Apparatus as claimed in claim 5 having at least one abrupt increase in cross sectional area intermediately along the passageway.

7. Apparatus as claimed in claim 5 having two adjacent passageways merging into one common passageway at an intermediate point along their length, said common passage being of no greater area than the sum of the areas of the merging passageways.

8. Apparatus as claimed in claim 1 in which the helical passageway is in the form of a hat spiral.

9. Apparatus as claimed in claim 8 wherein each unit has a plurality of concentric interleaved spiral passage- Ways which have their inlet and discharge ends circumferentially spaced.

10. Apparatus as claimed in claim 8 having its inlet end near the axis of said spiral and the discharge end at the periphery of the spiral, and liquid containing means located at the center of said helix whereby a plug of liquid is picked up by the inlet end of said passageway on each rotation.

11. Apparatus as claimed in claim 8 wherein the volume of each individual passageway within the boundaries of any sector of any unit is substantially constant, irrespective of where the sector is measured.

12. Apparatus as claimed in claim 8 having a plurality of said units secured together coaxially in side-by-side relationship, said fraction-collecting means being constructed and positioned to receive the liquid fractions discharging from all the passageways of all said units.

13. Apparatus as claimed in claim 12 where each unit has a plurality of concentric interleaved spiral passageways which have their inlet and discharge ends circumferentially spaced.

14. Apparatus as claimed in claim 12 wherein the volume of each individual passageway within the boundaries of any sector of any unit is substantially constant, irrespective of where the sector is measured.

15. Apparatus as claimed in claim 12 in which the passageways are four walled, a series of plate means perpendicular to the axis 0f said helix with adjacent plate means forming two walls of a passageway, and at least two wall means mounted edgewise on said plate means and curved to form between them a passageway in the form of a flat spiral and forming the other two walls of a passageway.

16. Apparatus as claimed in claim 15 in which there are more than two of said edgewise mounted Wall means to produce a plurality of identical concentric spiral passageways having outlets equally spaced around the circumferences of said plate means.

17. Apparatus as claimed in claim 15 including casing means in which said apparatus is mounted, and means associated with said casing means to receive separately fractions of liquid discharging from said passageways.

References Cited UNITED STATES PATENTS 3,396,850 8/1968 Kubat et al 210-322 FRANK A. SPEAR, J R., Primary Examiner 

